Analysis of fluid mixtures



June 8, 1937. B. MILLER 2,083,521

' ANALYSIS OF FLUID MIXTURES l Filed March 9, 1934 2 Sheets-Sheet l wud .N SMQRN. MN N N NN June s, 1937. B, MILLER 2,083,521

ANALYSIS oF FLUID MIXTURES Filed March 9, 1954 2 Sheets-Sheet 2 ANALYZER 72 Z? fg'' 34 REDQCING vGAS SAMPLE. oxnmzma GAS Y INVENTOR BENJAMIN MILLER ATTORNEY Patented .lune i,

UNITED STATE@ anni Para

GFFifE.

to Power Patents Company, Jersey City,

a corporation of Maine Application March 9, 1934, Serial No. 714,755

12 Claims.

This invention relates to the analysis of fluid mixtures and more particularly to the quantitative measurement of combustion components of gaseous mixtures of the type of flue gases which are produced in combustion operations.

It has been heretofore proposed to analyze qualitatively the gaseous products of a furnace combustion operation for the purpose of ascertaining the presence therein of an element of 1o combustion, by withdrawing a current of iue gas from the furnace, dividing the current into two branches cr streams, adding a combustion-supporting reagent such as oxygen or air to one branch and a combustibie reagent to the other,

l5 inducing flow of the branch streams over wires electrically heated to the ignition temperature of any combustible mixture in either stream, and

utilizing the change in electrical resistance set up in the respective wires by the differential heats of combustion of said streams to unbalance a Wheatstone bridge and to actuate mechanism for automatically controlling the supply of an element of combustion to the furnace.

A primary object of the present invention is to provide improvements in methods and apparatus heretofore proposed for analyzing fluid mixtures whereby to adapt same to a quantitative measurement of the excess of one of two mutually reactive components of the mixture.

Methods of the type above referred to for qualitatively analyzing gaseous products of combustion, have not made adequate provision for adjusting all ofthe variable and mutually related factors affecting the analysis so as to insure that any change in the temperature of the wires forming the active legs of the Wheatstone bridge which is not due to the presence of an element of combustion in the flue gas, must not imbalance the bridge. The temperature of each lo of the wires changes with a change in the temperature of the surroundings, or in the voltage of the source of. electrical energy, or with the thermal conductivity of the gas bathing the wires, or with theheat capacity of the gas bath- 45 ing the wires, or with the rate of flow of the gas over the wires. Moreover, the air or other combustion-supporting agent which is added to one branch stream has a thermal conductivity different than that of the flue gas and also different 10 than. that of the combustible reagent, such as hydrogen, which may be added to the other branch stream. The cooling effect of hydrogen is greater than the cooling effect of air at any particular temperature, and such cooling effect varies with i5 the temperature. Thus hydrogen has a thermal (Cl. #Z3-255) conductivity which is 7.35 times that of air at zero degree C., but only six times that of air at 100 C., and the heat capacity also changes with the temperature. Therefore when the amounts of combustible and combustion 'supporting reagents which are added to the respective gas streams are proportioned in accordance with their respective thermal conductivities and heat capacities so as to insure a balancing of the bridge at a given temperature of say 809 C., current will nevertheless flow through the galvanometer element of the bridge if the average temperatureL ofthe wire changes for any reason, and the amount of current flow will be greater the greater the change of average temperature in the wire. However, a deniteminimum current is required to make the galvanometer needle move over to the contact through which the combustion control mechanism is actuated. Therefore there will always be a definite temperature range in which the compensation between the thermal properties of the added combustible and combustion-supporting constituents, though not perfect, will be close-enough to keep the control mechanism from functioning.

An important feature of the present invention resides in passing sample streams of flue gas or other -fluid mixture to be analyzed for combustion elements, respectively over identical wires connected in series and similarly disposed in v identical surroundings or combustion cells, and. in adding small substantially thermally balanced increments of combustible and air or oxygen to the respective streams on the up-stream side of the cells. The smaller the volumes of the added increments of combustible and oxygen relative to the flow rate of the flue gases, the greater the temperature range through which their respective cooling effects are practically balanced. The

amount of added combustible or oxygen is preferably limited to that required to get an indication with the smallest amount of combustion element in the flue gas which it is desired will operate the instrument. Since methane causes the smallest galvanometer deflection per unit of heat content of the combustion elements which are commonly present in flue gas, it is usually satisfactory to adjust the ow rate of the added air or other combustion-supporting element relative to the flow rate of flue gas sample so as to cause the instrument to indicate when the flue gas contains the maximum permissible percentage of methane, at the same time adjusting the iicw rate of the added hydrogen or other combustible to balance the cooling effect of theadded percentagesoi methane, i. e. hundredths of a per cent, it is advantageous to use oxygen and carbon' monoxide respectively, asythe combustione vsupporting and combustible reagents. k

By using identical combustion cells (including Wires) and adding small quantities of .combusti-1 ble and air oroxygento the respective streams of flue gas on the up-stream side -of the cells, the

present invention is rendered 'independent 'of changes in average wire temperature, so long as the normal operating temperature is maintained somewhat higher than the ignition temperature of combustion components in the vflue gas sample, but not so high as toapproach the temper-f ature which causes rapid Volatilization of the wire. The galvanometer needle Will remain in al neutral position between the two contacts so longY as the flue gas sample contains neithei` combustible gas nor oxygen. When combustible gas apkpears inthe sample, it reacts with the'added oxygenonthe surface of one of the wires. This Acauses the temperature of that wire to increase,

f' thus increasing` 'the total resistance inthe cir" cuit. The current inthe circuit then decreases,

[which decreases the temperature Vof the.V other wire. Thus the wireon which combustion takes I placebecomes hotter, while the otherA wire becomes colder. If the difference in temperature lis'greate'r than'a certain minimum valuedependf ing on the operating temperature and the instrument constants, `sufficient current will flow Vthrough the galvanometer to cause the needle to make the appropriate contactjwhich will set the combustion control actuating l mechanism "into n operation. The sample'of flue gas may contain a large proportion of 'air or alarge proportion of s (combustible Without causing an'excessive temperature risein the wire, sincewhen the proportion of combustible in the sample exceeds Va certain value, the temperaturerise is limited `by the rate of addition of oxygen, which being small is safely below the danger point at which rapid volatilization of the wire-'takes place. Because lri'se which results from using` no more reagent `than is required to indicate the maximum permissible departure of the ilue gas from inertness, itis possible' to operate in the temperature range" of 1600 F. to 2000" F., in'nwhich range the sensitivity tomethane is highest.

Methods heretofore proposed for determining the'presence of a combustion element in )gaseous "combustion products are' notreliable when applied kto combustion products containing both combustible and oxygen or air.- Thus,if the lue gascontains high percentages of both oxygen and combustible by reason of an ineflicien't combustion operation, the rise of temperature which occurs in the wires of theWheatstonebridge an- .alyzermay be sucient to destroy the wires. 'It

both combustible and oxygen yare present in the ilue gas, "but-one is present in large excess,jthe galvanometermay function to show the excess.

` Butiffthe excess is small, the galvanometer may Ashowtlie excess, may show nothing, or may give the wrong indication. For example, the instrument maybeadjusted soV as to operate when the sample contains 0.1% methane, the balance bc- J ling inert. But if the` sample contains 2%'oxygen and 1.1% methane, which is a 0.1% excess of methane, and if the reagent added vis hydrogen, the galvanometer may'indicate an excess of oxygen, sincethe wire is much moresensitive 4 pletely reliable and vstood that the invention the practice of the invention as applied to qu to a hydrogen-oxygen mixture thenA to al methane-oxygen mixture of the same total potential combustion energy content.`

A more particular vobject of the present invention .is to provide methods and means for making 4,reliable qualitative analyses of gas mixturesof the type of flue .gas containing variable quantities of either or both combustible and combustion-supporting constituents.

Another importantr object of the invention is to provide method and means adapted for mak- ,ing reliable quantitative analyses of gas mixtures r of ythe type of ilue gas-containing variable quantities of either or both combustible and combustion-supporting constituents.

Other moreI specic objects of the inventionk 'Will yhave asubstantially permanent calibration throughout its periodof uscito provide a combustion gas analyzer employing a heatingfelement in an electric circuity in connection with which theneed ,for current balancing meansV has been eliminated; to providefor'maintaining the accuracy of a `combustion gas analyzer independentlyrof the presence of unburned hydrocarbon vapors or water vapor in the gases Vbeing analyzed; tov provide in novel manner for prolonging the eiective life of a catalytic element associated with a gas'analyzer operating under combustion principles; and to provide a novel combustion gas analyzer apparatus which is comoperative over a relatively wide temperature. range.

` `With the above and other objectsand features in view, the invention consists inthe improvements in inafter'described and particularly dened inthe claims. In its broadest aspect, the invention contemplates vboththe qualitativefand quantitative f analysis of a fluid mixture such as flue ygas which rmay contain both combustible and oxygen. Alof this protection against excessive ,temperaturen :ture undergoing analysis vis described ascomprising nue gases from a furnace, it will be underis broadly applicable to the analysis of fluid mixturesgenerally, and contemplates analysis of engine exhaustgascs. In

tative analysis, a measured sample of the flue gas Vtobe analyzed is passedthrough a combustion zone which is maintained lat a temperature at iluid mixture analysis which are here-4 which reaction will take place between combust- Y ibleand oxygen components 'of the ilue gas. The said flue gas sample isnthencooled and divided into two streams which preferably are equalv in mass or at least maintained in the same relative proportions. To one `ofthe said portions there is added a relatively small` regulated amount of Va combustible such as hydrogen, and to the other portion thereis added `a relatively small proportion of aV combustion-supporting'iiuid such as air.

VThesetwo portions of the gas are then simultaneously passed into contact'respectively with separate highly heated Wires 'similarly disposed in separate identical combustion cells. The added portions of hydrogen and airshould substantially balance eachother with respect to their cooling effect on the wires.. Combustion of any combustion element present in excess in the flue gas sample takes place in one of:the cells, generating heat unequally in the cells. Visual evidence of the heat unbalance of the cells may be indicated by a galvanometer disposed in circuit with thermocouples mounted in the cells.

Quantitative analysis of the flue gas is preferably effected by adding to the flue gas sample before it enters the first named combustion zone a measured amount of a reagent which reactive with a combustion component of the flue gas known to be present in excess, to bring the temperature-s produced in the respective analyzer cells in balance. The amount oi the reagent thus required to secure a heat balance betweenlthe analyzer cells is then measured by a flow meter in terms of the amount of excess combustible or combustion-supporting 'components in the ue gas under test, as will hereinafter be more fully described.

The invention will be hereinafter described more particularly by reference to the accompanying drawings, in which:

Fig. 1 illustrates diagrammatically apparatus designed for use in determining the presence of an excess of a combustion element in a gas mixture by a qualitative analysis;

Fig. 2 illustrates diagrammatically apparatus designed for use in measuring the excess of a combustion element in a gas mixture by a quantitative analysis; and

Fig. 3 illustrates diagrammatically, a preferred embodiment ci the invention designed for use in measuring the excess of a combustion element in a gas mixture by a quantitative analysis carried out under my titration principle.

Referring more particularly to Fig. 1 numerals IB and i2 designate identical tubular combustion cells having their lower ends connected respectively with mixing chambers Ill and Iii by conduits I8 and 2). The cells Ill and il. have gas outlets 22 and 24 on their respective upper ends. Mixing chamber i4 has a gas inlet in the form of a fixed orifice 2li in one wall thereof, and mixing chamber IS has a gas inlet in the form of a fixed orifice 28 in one wall thereof. The orifices 26 and 28 are constructed so that gas flows. therethrough from a supply chamber 3S at an equal or uniformly proportioned now rate at all times. Secured within cells IE! and i2, respectively. in identical relation with the cell walls, are identical resistance heating elements and 34 in the form of coil filaments of refractory metal which may have catalytic properties or may be catalytically inert. It preferred to use platinum or rhodium, or platinum-rhodium alloys, in the construction of coils 32 and Zit. In the form shown in Fig. l, coils 32 and it are connected in series with a source 3E of house current, b f means of lead wires 33 and dil.

Cells It and i2 combustion cells of a gas analyzer which is particularly designed for mal:- ing qualitative analyses of flue gas for 'the purpose oi ascertaining whether such gas contains an excess of oxygen or an excess of incempletely burned combustible such as CO. In order to feed a sample stream of flue gas to each of the cells It) and l2 through the supply chamber 3Q, a pump 4?. is provided having its suction inlet all connected through a filter chamber l and through a conduit 48 with the exhaust gas iiuc oi a :furnace 5i). Discharge outlet 52 of pump 42 is connected by a conduit 5ft with supply chamber 30. Pump 42 is shown as embodying an eccentrically mounted slotted rotor with freely `slidable blades cooperatively engaging tbe inner surface of the pump wall, the rotor being keyed to a drive shaft 56. Two other similar pumps 58 and 6U are shown in Fig. 1 as also keyed to shaft 55; shaft 55 being powered from an electric motor V62 which in turn receives its energy from source 36. Pump E@ is connected to draw air or other suitable combustion-supporting reactw ant from a source of supply through a filter G4 and to force air thus drawn through a conduit 6 into a chamber 68 from which a regulated small portion of air discharges into mixing chamber lli through a fixed orice lf3. Similarly, pump 58 is connected to draw a combustible reactant such as hydrogen or CO from a suitable source of supply through a filter l2, and to force such combustib-le reactant through a con"uit lli into a chamber l, from which a regulated increment thereof discharges through a fixed oriiice "i8 into mixing chamber I6.

Filters 45, 64 and 'l2 contain cotton or other suitable filtering material` adapted te separate solid or liquid impurities therethrough. Each of pumps 22, 58 and 6d is provided on its discharge side with a back pressure regulator and relief valve designated respectively '80, 82, and S4, whereby the gas pressure on the down-stream side of each pump is maintained approximately constant, and any excess gas handled by pump d2 is vented to atmosphere, or in the case of the gas handled by pumps 58 and till, the excess is returned to the suction side of the pump. Mounted in conduit 54 on the down-stream side of pressure regulator Zil'l and on the up-stream side of chamber 3Q, is a heat insulated combustion chamber tl'. This chamber is lined with quartz or other high temperature refractory material, and is provided with an electric heating coil 88 connected in thev aforementioned heating circuit 4E. The interior oi chamber 8E is preferably nlled with a combustion catalyst 9B such as platinized silica or platinum gauze. Between the downstream end of combustion chamber 86 and the analyzer supply chamber 3B, conduit 54 is provided with a plurality of heat radiating fins 92 or equivalent cooling devices for reducing the temperature of the gas leaving chamber 86 to a point where it will not endanger the resistance heating elements enrl ployed in cells I0 and I2.

n the practice of theinvention as thus far described, a clean sample stream of flue gas is forced by pumps 42 at a substantially constant rate through the electrically heated combustion chamber 85 and thence, after division into equal or constantly proportional portions, into mixing chambers I4 and Ill. As the flue gas passes through chamber 86 a combustion'reaction takes place between any combustible and combustionsupporting components of the gas thereby insuring that the ratio of excess is great between the combustible andl combustion-supporting components. Thus a iiue gas sample entering chamber 8E may have therein 2% oxygen and 0.2% methane. After passing through chamber 36, the methane content ci the gas should be reduced to substantially zero, and the oxygen content to approximately 1.6%, but the excess ratio of oxygen to methane has been greatly increased. From chamber 35 the thus treated gas sample passes through a cooling zone 92 into supply chamber 3&3, and thence in equal portions to the mixing chambers I4 and I5. Simultaneously air is forced into chamber `Ill in a regulated small increment by pump 60, and a combustible gas such as hydrogen is forced into chamber ill in regulated small increment by pump 58. The quantities of air and .hydrogen added to the respective portions of the from the gases passed y DI) ue gas sample in chambers I4 and I6 are rela.-

-tively small, and` may for example befrom 0.5%

to 5% by volume of the iiue gas portions introduced into these chambers respectively through l can be secured by calibrating the air and hydrogen flows .when passing through the analyzer 'a flue gas which contains neither combustible nor combustion-supporting components. 'I'he rgas mixtures then flow through the respective `cells I0 and I2, where they come in contact with the highly heated resistance elements' 32' and 34. 'I'he elements 32 and'34'4 are heated to a temperature well above theignition temperature -of any combustionelements in the gas mixtures owing through the cells, thereby insuring., combustion whenever combustion elements are present. Thus the Wires are heated to a temperature Vwhich will hold WiresA 32` and 34 in the operating range of 1400". to 2000 F. under Calibrating conditions when air aloneY is flowing'therethrough. `Any difference in energy developed in cells I0 and I2 i is measured by a thermocouple circuit 94 having hot and cold junctions mounted respectively in Cil opposed E. M. F. relation within cells I0 and I2. Any diierence in temperature developed in cellsl I0 and I2 will set up iiow of current in circuit .94 through-a galvanometer 96, thus'l causing the galvanometer needle to swing to the left or right. 4If the galvanometer needle `swings to the right it will indicate for'example, the presence of an excess of,combustible in the flue gas sample unv der test; and when the swing is substantial the needle may close the circuit of a power relay 98 which in turn `actuates through another relay 99 a switch |00 closing the circuit of a motor supply line |04. When the supply of air tothe furnace has thus been increased, the amount 'of excess combustible in the flue gas sample cor-respondingly drops; atwhich time the galvanometer needle may swing to the left'and break contact with power relay circuit 98, whereupon the combustion control mechanism will cease to function until a sufficient excess of eitherair'or combustible againdevelops in the flue gas sample to again close the power relay circuit and actuate ,the combustion control mechanism.v For the purpose of notifying an operator of the general qualitative*characteristics off-the ue gas under test, small light circuits may shown for closure by 'means of the relay switches |0| and |03, to apprize the operator when the gas is neutral and when it contains an oxygenor an excess'of combustible.

.One of the outstanding advantages of the qualitative combustion analyzer hereinbefore described and illustrated in Fig. 1, is the wide temperaturerange Within which itwill'operate. While it is preferred to have the temperature of the heating wires 32 and 34,-in the range of 1800 F. to

2000o F., particularly'incases where small concentrations of methane are to be detected, 'nevertheless the analyzer will operate satisfactorily anywhere within va vtei 1400 F. and 2400 The arrangement of the qualitative analyzer of Fig-1 can'be modified as illustrated 4in Fig. 2, toadapt it for quantitative analysis, by substituting a calibrated galvanometer in place ofv the galvanometer 905 of Fig. l, and by including mechanism for maintaining constant temperatures in, and rates of gas flow Vsure regulators B0, 82,`and 84 at the same pressure in order that there may be# be connected asV I 34 of Fig. 2 from a source' 36 excess of perature range between y through, the analyzer device.' One big advantage of the qualitative: analyzer of Fig. 1 resides in the factV that it .operates independently of changes in currentflow through the heating coils i and independentlyof changes. in rate u,

to insure that the sample'owrate be large as.,

compared to the ilowfrate of the added air and combustible gasreagents.'` So long as this rela tive flow relation is maintained between the ilue gassamples and the added reagents, relatively large uctuations in the ilow rates of the indi-`v vidual gases through the analyzer cell will not affect the reliabilityr of the analyzer readings. vIn other Words, the regulators 480, 82 and 8,4,n`eed maintain only approximately constant back pressures, and any iiuctuaticns in iiow rate which are caused 4by changes in the speed of motor 62 o1' by changes in flow resistance through the catalyst i bed S0 will not adversely affectzthe readings of the The `control of the analyzer any more thanwill changes in tempera- It is three back presture oii the gases delivered to the analyzer.` convenient, however, to have the nobackow of any of the gases into the supply line oi one of the other gases.

)Referring now more particularly to the quantitative continuous analyzer which is illustrated in Fig. 2, it will be noted that the cells the orificesv 26, 28, 'i0 and 18, together with the mixing chambers I 4v and I6 and the connecting conduits I8 and 20, are all mounted in a thermostat IIE! provided with an electric heaterl I2 havset todeliver gas` I0 and I2 and ing an automatic thermostat switch'l I4, by means of which the temperatures of the `gasentering each of the analyzer cells are keptconstant ata,

temperature higher than that of the surrounding atmosphere.l

of ilow of each .of Ythe gases entering mixing chambers I4 and I6 constant, quantitative pressure regulators 80, 82 and 84 are in each case 'directly connected with the chambers 30, l68 and orifices 26, 28, 'I0` 26 on the upstream side of and 18. 'The pressure regulators 80, 82, and 84 must/be more accurate and precise in operation than those used in the corresponding of Fig. 2 must be very nearly constant, for which reasona synchronous motorispreferred. Electric current is preferably supplied to down transformer 6 having constant current characteristics, and4 through ballasty resistances IIB. As previously indicated,V the quantitative In order to maintain the `rates K l analyzer of'y Fig. 1, and in addition 4the vspeed of motor 63 coils 32 and through a stepanalyzer of Fig. 2 vemploys `a calibrated 'galvanometer |20 in the thermocouple circuitA 94.

The operating temperature range of the calif Y brated quantitative analyzer ofFig. 2 is necessarily verynarrow. The qualitative analyzerV of Fig. 1 operates over a wide temperature range for the reason that the amount of combustible reagent which isaddedto the gas entering one combustion cell, and the Aamount'of air or oxygen added to the gas entering the other" cell, is'relatively small as compared to the volume of the gas;

and the amounts of added combustible reagent and oxygen should substantially balance with re- `spect to cooling effect Aover a wide temperature range. f When the method is'adapted to quantitative analysis, the amounts of added reagent cannot be very` small, since the amountof added! oxygen must be equivalent to the highest concentration of excess fuel which will be at any time present in the flue gas sample, or otherwise the galvanometer would not deect proportionally with an increase in fuel content of the sample. Likewise suiiicient combustible must be added to the sample to react with the highest concentration of excess oxygen which may be present in the sample. Moreover, the galvanometer needle should remain at its zer.; position when the sample contains neither excess oxygen nor excess coinbustible. Therefore the cooling eiiect of the added air or oxygen must balance the cooling effect of the added combustible. This limits the operating temperature of the instrument within a narrow range, since thecooling eiect of each of the added reagents changes with the operating temperature, and the changes are not proportional. Moreover, the operating temperature range is further limited by the iactthat the sensitivity of the instrument, as well its calibration, changes with the temperature. Thus the instrument might be calibrated to give a scale reading of 100 for 1% CO in the flue gas sample at 500 C. Ii for any reason the Wire temperature should increase from 500 C. to 600 C., the scale reading would drop to about '76 for 1% CO. Conversely, if the temperature should drop to 400 C., the scale reading would rise to about 138. Therefore the quantitative analyzer of Fig. 2 can be depended upon for measuring the concentration of excess combustible or excess oxygen only when operating in a limited temperature range. The nature of the combustible must'nct change and the nature of the inert gases must not change. For satisfactory operation, it is necessary to maintain substantially constant the supply of current to the analyzer heating elements, the rate of flow of the sample, the rate of iiow of the added combustible reagents, the rate ci iiow of the added combustion-supporting reagent, and the operating temperature of the combustion cell.

The apparatus illustrated in Fig. 3 represents a quantitative analyzer which is a practical improvement over the` analyzer shown in Fig. 2. The quantitative analyzer of Fig. 3 is designed for operation on the titration principle of continuous quantitative gas analysis, which underlies the invention described in my copending application Serial No. 650,133, led January 4th, 1933. The method of analysis for which the apparatus of Fig. 3 is adapted, is entirely independent of changes in current supply to the analyzer heating element, and is also independent of changes in operating temperature of the analyzer cells and of changes in rate of flow of gas sample and of combustible and combustion-supporting reagents through the instrument. In principle, the method of analysis which is practiced in the apparatus of Fig. 3 consists broadly oi adding to a flue gas sample the quantity of air required to exactly combine with any excess combustible in the sample, or the quantity of combustible required to exactly combine with excess oxygen in the sample. This titration is carried out automatically and the percentage of excess oxygen in the sample is determined by hydrogen, for to a unit quantityrof the sample, in order. to neutralize the sample. The method and apparatus oi the qualitative analyzer illustrated in Fig. 1 affords a reliable determination as to whether the flue gas sample is neutral or contains excess oxygen or excess combustible. This determination is then used as a basis for a timeasuring the amount of' example, which must be added tration :determination of the amount of such excess. The titration method of analysis for which the apparatus of Fig. 3 is adapted is of particular utility `for analyzing a gas such as the ordinary 'furnace fluegas, the composition of which is likely to change frequently from hav-v ing an excess of oxygen tohaving an excess of combustible.` l

In thexoperation of .thejapp'aratus of Fig. 3, a. sample of flue 'gas is drawn from the furnace through conduit 43, filter 46, pump B2, and thence is' forced throughy A*combustion chamber 86 into a supply chamber 30, from which equal portions' pass through.- .orifices 2S and -28 into mixing chambers id, and IB'.l and thence through. identical analyzer cells Il) and l2. Simultaneously, air' is forced by pump 60 through` orifice 10 into mixing chamber |4- from whence it passes in admixture with oney portion of the ilue gas sample through cell i0. At thefsame time a combustible gas reagent such as hydrogen is forced by pump 58 through orifice i8Y into mixing chamber lt, and thence in admixture with the other portion ci flue gas sample through combustion chamber l2. If the temperature developed in cell |U is greater than the temperature developed in cell i2, the i'lue gas sample contains excess combustible, and the, needle of galvanometer 96 will indicate the presence ,of suchv excess by swinging to. the right@ The contact made by the galvanometerwill close the circuit of power relay S8, and will thereby energize one of the solenoids 924i of a reversing mechanism |22. In addition to the solenoidsi2| which are energized by power relay 9B, the Vreversing `mechanism |22 embodies as elements a rocker crank |24 which is journ naledon a shaft |26 `and which is powered from shaft 550i pump motor 62 through a pinion |28, rneshingwith -a gear crank i3d, from which a reciprocating-motion isimparted to crank |24 throughconnecting rod |32. When the proper solenoid|2| `of reversing mechanism |22 is energized'by `theneedle of galvanometer 96 swinging to the right, an armature member |34 which is pivotally mounted onv the solenoid frame is rotated inl a counter-eloclnvise direction about its pivotal support by the lattraction of the electric eld oi the solenoid. A pawl |36 ,is rotated clockwise on its pivotalsupport on rocker arm |24 and thereby brought rst into and then out of engagement with the. .teeth of ratchet gear |38, each time crank arm Zll reeiprocates.- A coil spring ifi@ normally noids armature |311 and pawl |36 in the disengagingposition illustrated, except when the solenoidsof mechanism |22 are energized throughpower relay 98.

When the galvanometerneedle swings to the right as previously described in response to the presence of van vexcess of combustible in the flue gas sample, mechanism |22 operates through ratchet gear 138 to slowly rotate shaft |28 in a clockwise direction, thereby opening a valve |42 in a cross connection |44 between air supply pipe 5t and gas'sample supply pipe 54 on the upstream side of catalyst 'combustion chamber 86. This results in the addition of air to the gas sample entering the combustion chamber 86, and the air thus added'combines with excess combustible inthe sample during the passage of the sample through catalyst chamber B6, so that when the thus modified sample reachescell l0 there has been a decrease yin the amount of combustible in the sample equivalent to the amount of air added bythe opening of valve M2. When the amount of air added to the gas sample by the.- openin'g of valve |42 is just suillcient to `burn l Y, eutany-excess combustible in the sample; the

thus modied sample entering mixing chambers I4 (and 6 will be neutral, and thisl neutrality 5 will act lthrough galvanometer 96 and theipower relayl98 to-'disengage pawl |36from-ratch`et .|38,fv

thereby arresting. further opening of valve |42.

1 It willbelnoted rthat the adjustment ofyalve` |42 isa step by stepadjustment effectedjby 0 theintermittent motion imparted to shaft |26 and'ratchet |38 by the mechanism |22.' A spring brake |46 operatively connected with shaft |26 serves to prevent vrotation of the. shaft except when; actuated through ratchet |38. `'I'heslow 5 intermittent step-by-step motion imparted to the shaft |26 1andvalve` |42 is preferred in order to avoid over-'control andhunting.

The quantitative analysis of the flue gas sample is made byv a -titration principle previously re.-

0 fel-red to. According to'thismethod, the volume u of air which valve |42 must pass in order to neutralize the excess combustible content of the gas flowing into combustion zone'86 is metered by a differential flow meter |48 connected across ori- 5 iice' |50in the air conduit |44 on the up-,stream side of valve 42. The opening of valve |42 is cifcctedthrough the mediumof a cam |52 which on clockwise rotation of shaft |26 raises the stema*k of valveil42: Counter-clockwise rotation ofthe y 0 cam v|52 'allows a valve spring |54 to close valve` |42. r Flow meter |48 measures the-amount of air or oxygen required to neutralize excess combus-` tible in the vflue gas sample, Athe meter being preferablyl calibrated in terms of ratio of flow of air passed by orifice |50 toratio of flow of gas sample passed by orice 56 in the gas sample supply line.

i Thus, if therate'of ow of the sample past orificer regulator 80, and by maintaining a constant pres-x` suredrop across the orifice by meansof a pressure regulator |58 actuating a relief valve |60-on the downstream side of the orifice.A ,The pressure regulator 84acts to maintain a constant. airtpressure on the upstream sideI of air supply orifice |50, `All that is necessary in the operation of this apparatus is to maintain ar relatively constant ratio between the ow rate of flue gas sampleA and the flow rate of the added reagent. In this re'-A spect the apparatus of Fig. 3 Idiilers from that of combustible. No temperature control is required other than that of keepingthe'temperature of the flue gassample and that of the reagentthe same at the respective orificesy |50 and 56. This is automatically accomplished for the reason thatj the gases at this pointare both substantially at atmospheric temperature. Y

When the ue gas sample'carries excess oxygen ratherxthan excess, combustible, the needle of galvanometer 96 will swing-in the opposite direc-v tion thereby actuating through power relay 98 the other solenoid |2| of reversing mechanism aosasar Y presence of an excess of Fig.'2`,in which an absolute constant ratio must c be maintained between the flow rates'of the flue Y gas sample `and the flow rate of theadded air or4 |22, thereby rotating shaft |26 step-by-step in a counter-clockwise direction. The counter-clock` wise rotation of shaft |26 actsthrough cam |52` to first close valve .|42,' and then through a cam between combustible 'reagentsupply pipel 14 and uegas conduit 54.Y Theamount of combustible gas such as hydrogen which it is necessary that valve |64 shall pass in order to neutralize excess oxygenrcontained intheue gas sample, Vis then `measured by a differential flow meter |68 con-Y nected, across an oricerl'l in.V pipe |66. The. valves which control the supply of air and fuel to i fthe furnace from 4which thefflue gas sample is taken, may be automatically controlled by means such for example as the `reversing mechanism |22 acting through anextension'of shaft |26 (not shown). In other wordsv the reversing mechanism may be madethe connecting link whereby combustion in theA furnace is` automatically controlled in accordance with the analysis of the flue gas which is-made byanalyzer cells I0 and |2.

'Thespecd reduction ratio between shaft 56 and rocker arm |24 isy preferably `so adjusted l(as by varying the speed ratios' of pinion |28 and gear |30) that the rockerarm reciprocates once during the period consumed in passing a unit volume of the gas or other fluid sampleunder test from orifice |56 throughthe analyzer, and in completing ,the analysis. 'I'hus -if after analysis has i shown that a sample of the ue gas contains4% excess CO the composition of the ue gas should change so that thefCOcontent drops to 3%, the

analyzer would almost immediately indicate the I oxygen in the gas stream leaving combustion chamber 86 resulting from theaddition .to the gas of more air than that necessary to combine with the COvnow present in the sample. The higher temperatures developed in celli|2 would now cause the galvanometer needle to swing to the left and `thereby actuatethe reversing mechanism |22 to4 u The rotation l of the shaft would be so slow` as to arrest the@ point where the air` passed'thereby will substantially balance the re` ducedA CO content in theflvuergasdeliver'ed to rotate shaft |26 counterclockwise,

closingrof valve |42 at the combustion chamber'86 through orifice |56. It will be understood that cam|62 does notoperate to open valve |64 until'valve |42 has been enstream through valve |42 c tirely closed by rotation of shaft |26 acting through cam |52.

In place of the two differential meters or presf c sure gauges |48 and |68," a singledifferential pressure gauge mayV be'substitutedv having two pressure taps, one connected to the up-stream side of valve |42 andthe other to the up-stream side of valve |64. Y

VBy subjecting the the intensities of any reactions which may later take `placein cells |0 and `|2 may be more accurately measured withoutthe possibility of injury totheheating elements or thermocouples by development of excessively 'I'he invention as described isfalso adapted for the measurement of reactive componentsof fluid` mixtures by the addition thereto of fluid react-Y antswhich produce endothermic instead of exo- A thermic reactions. Y i 1 VIt is notpessential that wire heating elementsi beemployed within the cells I0 and |2, nor` is` it essential that catalytic material be employed in combustion chamber 86. All thatisnecessary is y that conditions favoring combustion be maingas {sample to temperatures. favoring combustionin combustion chamber `86,`

high temperatures. A i

cof

tained by some means in chamber 8B and in cells Iii and I2.

It will also be understood that only a part of the gas passed through combustion chamber 86 need go to the analyzer cells Iii and I2; and that the iiow meters it?) and lilof the apparatus of Fig. 3 are the only elements thereof which need be calibrated, and this calibration need not be a made in place if the proper type of differential meter is used. The titration method of analysis underlying the apparatus of Fig. 3 not only opcrates` independently of uctuations in all operating factors except the composition of the fluid mixture being measured, but it is also advantageous in that there is no great time lag between the operation of the combustion analyzer and the moment that the indicating mechanism is actuated to record the composition of the fluid mixture under examination by the analyzer.

The invention having been thus described, what is claimed as new is:

l. The method of determining which one of two mutually reactive components is present inexcess in a gaseous mixture, which comprises subjecting a continuously flowing sample of said mixture to conditions under which reaction takes place between said components so as to increase the ratio of the excess component to the deficient component, dividing the resulting reaction mixture into two uniformly proportional streams, adding a small increment of a gas reactive with one of said components to one stream, adding a small increment of a second gas reactive with the other component to the other stream, employing a sufficient volume of the increment gas which reacts with the excess component of the gas mixture to give an indication of the presence of said excess component, proportioning the volumes of said added increments with relation to each other so as to balance said increments with respect to their thermal capacities and heat conductivities, passing the thus modified streams through identical reaction zones while subjecting the streams to uniform conditions under which reaction takes place between the components and the gases reactive therewith, and indicating any difference in the intensities of the resultant reactions in the respective gaseous streams.

2. The method of determining the amount of excess of one active component in a continuously flowing measured stream of a gaseous mixture which may contain two mutually reactive componente which comprises, adding to said mixture a reagent reactive with said one active component, reacting said reagent and said component, dividing the reaction mixture into two uniformly proportional portions, adding to one portion a small increment of said reagent, and simultaneously adding to the other portion a small increment of a second reagent which is reactive with the first reagent adjusting the volumes of said added increments so as to balance their thermal capacities and heat conductivities, concurrently subjecting th thus modied portions of the reaction mixture to conditions under which reaction takes place between the reactive components and the added reagents, measuring the difference in the intensities of the resulting reactions in the respective gaseous portions, adjusting the amount of first-named reagent added to the original gaseous mixture so as tobalance the intensities of the last named reactions, and measuring the amount of said rst named reagent thus required.

3. The method of determining the amount of excess of one combustion element in exit gases from a combustion operation which may contain another combustion element reactive with the former, which comprises adding a measured amount of a` iluid reactive with said first named combustion element to a continuously flowing measured sample stream of said exit gases, heating said stream to a temperature favoring reaction between said fluid and said element, cooling the reaction mixture and dividing it into two uniformly proportional portions, adding to one portion a small increment of combustible and simultaneously adding to the other portion a small increment of a combustion supporting gas, the volumes of said added combustible and combustion supporting gas increments being substantially balanced with respect to their thermal capacities and heat conductivities within the reaction temperature range, concurrently subjecting the thus modified portions to temperatures favoring combustion reactions, measuring the difference in the intensities of the resultant reactions in the respective gas portions, adjusting the amount of reactive fluid added to the original gas sample so as to balance the intensities of the final reactions, and measuring the amount of fluid reactant thus added in terms of the amount of said combustion element with which it reacts.

4. The method of measuring the amount of a reaetant in a iiuid mixture which comprises adding to a continuously flowing measured of the mixtiu'e a second reactant, subjecting the resultant mixture to conditions under which said reactants become mutually reactive, dividing the resultant reaction mixture into two uniformly proportional portions, adding a small fixed increment of a fluid reactive with one of said reactants to one of the said portions, adding tothe other portion a small fixed increment of a fluid reactive with the other reactan proportioning the volumes of said added increments so to balance said increments ith respect to their thermal capacities and heat conductivities, concurrently reacting the respective portions in separate reaction zones thereby producing heat of unequal intensity in the respective zones, adjusting the amount of the second reactant added to the fluid mixture so as to balance the temperatiuies developed within the said reaction zones, and measuring the amount of second reactant thus required.

5. The method of measuring the extent of an incomplete chemical reaction which comprises, mixing a continuously flowing measured stream of a iluid product of the reaction with a regulated amount of a Second iluid reactive with a component o-f the fluid product, reacting the fluid mixture under conditions substantially to reduce the amount of one of the reactive compon-ents and form a residual reaction mixture, dividing the residual reaction mixture into two uniformly proportional portions, adding to4 one of the said portions a small increment of said second reactive iiuid, adding to the other portion a small increment of a fluid reactive with said second reactive fluid, proportioning the volumes of said added increments so asl to. balance said increments with respect to their thermal capacities and heat conductivities, thereafter concurrently subjecting the said fluid portions to conditions producing reactions therein, measuring the intensities of the last-named reactions in the respective uid portions, adjusting the amount of the second reactive fluid added to the action mixture into two mixture, tworeaction ture thus formed `under conditions substantiallyv the lamount of one ofthe reactive reaction mixture,

to reduce iiuids and` to form a residual dividing the said reaction mixture into two unii formly proportional portions, adding to each ofV said portions a small fixed increment of one of two mutually reactive fluids; each of which isV reactive f with Yone of said first-,named Iluids, thereafter concurrently subjecting the said fluid portions to similar conditions producing rea-ction therein, developing opposedv electromotive forces varying respectively in response to variations in the intensity of reaction in the respective portions, noting the direction of the resultant electromotive forcefadjustingthe amount of the second reactive fluid so as to balance the intensities of said reactions, and measuring the amount of the second fluid thus required.

'7. Apparatus adapted for analyzing a continuously Iiowing sample streamof a :duid which may contain two mutually reactive components for the lpurpose of measuring the amount of excess of one of'said components which comprises, means for mixing with' said; first-named iiuid a second uid reactive with the component which is present in excess, a reaction chamber in which said mixture is subjected to temperatures favoring reaction between said second fluid and said component, means for dividing the resultant reuniformly proportional portions, a device for modifying one ofthe `said portions by introducing thereto a small fixed increment of a iiuid reactive with one of said activeL components, a device for similarly modifying the other portion by introducing thereto a small fixed increment of a fluid adapted to react with the other active component of said cells, means for directing one of said modified porti `ns into one cell, means for directing the other modified portion into the other cell, means for indicating any difference in temperature developed in the two cells, and calibrated means for regulatingv and measuring the amount of second reactive fiuid which is added to the'first-named fluid stream in order to balance the temperature developed in the cells.

8. In combination, means for continuously forming aregulated mixture of Waste combustion gases and a gaseous element ofcombustion, acombustion chamber and means for` `subjecting said gas mixture to temperatures favoring combustion reactions therein, means adapted to divide combustion gases leaving said combustion chamber into two uniformlyproportional portions, a device for mixing with one of said portions a small iixed increment of `a combustionsupporting gas,ja second device for mixing with "the other portion a small fixedy increment of ay combustible gas, two combustion cells, means for separately conductingA the respectiveportions to corresponding cells,.means adapted to measure I any temperature differential between the Vrespective cells, and calibrated meansfor Vmeasuring the volume Vof combustion element added to the waste gases vin order to balance the temperatures developed lin the cells; Y

zones, thereby producing heat 9. The method. of determining whether the" gaseous products of a combustion operation contain an excess of a combustible gas or an excess o fV oxygen, uously ilowing stream of said products to a temperature under which combustion reaction takes place between said combustible gas and said oxygen so as to increase the ratio of the excess constituent to the deilcientconstituent, dividing the resultant products of reaction into two uniformly proportional streams, adding a small increment of Van oxidizing gas such Yas air to one stream, adding a small increment of acombustible gas such as hydrogenv to the other stream, proportioning the volumes'of said added increments so as to balance said increments with respect to y their thermal capacities and heat conductivities,`

passing the thus-.modified streams throughiidentical combustion 'zones while subjecting' the streams to uniform` conditions of temperature under which combustion. reaction takes place, andV indicating any difference in the intensitiesof the resultant reactions in the respective streams. 10. The method of determining the amount oi lexcess of oxygen in they gaseous products of ra combustion operation which may also contain which combustion reaction takes place betweenv said oxygen and which lcomprises subjecting a contin.`

of combustible gas, proportioning the volumes of f said added increments so as to balance said increments with respect to their thermal capacities and heat conductivities, concurrently subjecting combustion in separate identical combustion of unequal intensity in the respective zones, adjusting the amount lthe respective portions 'to conditions supporting 1 of combustible gas added to the original gaseous products so as to balance the temperatures developed withinthe said combustion zones, and measuring the amount of combustible gas thus required in terms ofthe amount of oxygen with which it reacts.

11. The method of determining the amountof excess of a combustible gas in the gaseous products of a combustionroperation which may also contain oxygen reactive with the combustible gas, which comprises adding a measured amount of oxygen to ajcontinuously flowing sample stream of said combustion products, heating said stream to a temperature at which combustion reaction said oxygen and said comsaid combustion reaction and dividing the stream into two uniformly proportional portions, adding a small yfixed increment of a combustible gas tov one of said portions, adding to the other portion balance said increments with respect to their the stream of products of i thermal capacities and heat'conductivities, concurrently subjecting the respective portionsl to conditions supporting combustion in separate re'V action zones thereby producing heat of unequal intensityin the respective zones, adjusting the Y 'amount of oxygen added to the gaseous products of combustion so as to balance the temperatures developed Within the said reaction zones, and measuring the amount of oxygen thus required.

12. In apparatus for analyzing Waste combustion gases for unburned combustible, a combustion chamber and associated heating elements for maintaining temperatures forming combustion reactions therein, means for continuously forming a regulated mixture of waste combustion gases and a combustion supporting gas and introducing said mixture to said chamber, means adapted to withdraw a stream of products of combustion from said chamber and to cool the same, means adapted to divide said stream of products into two uniformly proportional portions, a device for modifying one of the said portions by adding thereto a small xed increment of a combustion supporting gas, a second device for modifying the other portion by introducing theretoa small fixed increment of a combustible gas, said device being arranged to balance the volumes of added increment of combustion supporting gas and combustible gas with respect to their heat capacities and heat conductivities, means for adjusting and. measuring the relative proportions of the Waste combustion gases and combustion supporting gas owing to the first named mixing means, two combustion cells, means for directing one of the said modiiied portions through each cell, and means for indicating any difference in temperature developed in the tWo cells.

BENJAMIN M'ILLER. 

